PELECYPODA 581 



2. Strophitus* Rafinesque. Shell inflated, rounded, with a hard, 

 shining periostracum ; teeth rudimentary, consisting of an irregular ridge 

 in the left and 1 or 2 faint ridges in the right valves; male and female 

 shells alike; glochidia not parasitic: 8 species, all American. 



S. edentulus (Say) (Fig. 913). Shell ovate, hinder margin fonns 

 an obtuse angle with dorsal margin ; umbo but little in front of the mid- 

 dle; interior, bluish-white; surface yellowish, Avitli dark rays; lengtii 8 

 cm.; height 4 cm.; width 3 cm.: eastern and central states. 



3. Anodonta Lamarck. Shell thin, oval or elongate, inflated; peri- 

 ostracum generally smooth and without rays; hinge without teeth, regu- 

 larly curved; cloacal siphon without papillae; male and female shells 

 alike: 55 species, 30 American, the animals living usually in muddy 

 streams and ponds, often buiied in the mud. 



Key to the species of Anodonta here described: 



Cj Shell large. 

 hi Dorsal margin straight A. catabacta 



62 Umbo with undulating wrinkles A. grandis 



63 Shell with very thick margins A. imptjcata 



Qa Shell small and bright green A. imbecilis 



A. cataracta Say (^1. fluviatilis Gould) (Fig. 914, A). Shell oval, 

 large, crested behind, deep green in color, with obscure radial rays, 

 white within, with a lilac tint; hinge margin straight; 11 cm. long, 7 cm. 

 high, 37 mm. wide; shell 



rounded in front and form- ^<:::^^^^'^/''"'^"'*-^==^^^^^^^:::^^^^^^^^^^^ ^ 



ing an obtuse angle behind: ^^^ ^.^7 ^ ^^"^^b 



Atlantic slope, south ^^ If f f -n 



North Carolina; common. 



A. grandis Say (Fig. 

 914, C). Shell elliptical, in- 

 flated, green or black in 

 color, with usually faint p. g^^ 



rnrlinfirnr rnvs; 1 '^ oxx\ lono- A., Anodonta cataracta (Gould) ; B, A. implicataj 

 radiatmg ra\S, l- cm. lon^, , ^^ ^ grandis; D, A. imhecilis (Baker). 



7 cm. high, and 5 cm. wide, 



or larger; umbo marked with about 5 elevated undulating wrinkles: 



central states; common. 



A. implicata Say (Fig. 914, B). Shell oval, thick and heavy, with a 



rough, light yellowish-green outer, and a pmk inner surface, 10 cm. long, 

 56 mm. high, and 35 mm. wide ; hinder end with a truncated point which 

 is joined with the umbo by a very pronounced edge: Atlantic slope as 

 far south as Virginia ; valley of the St. Lawrence. 



* "Metamorphosis without Parasitism," etc., by G. Lefevre and W. C. Curtis, 

 Science, N. S., Vol. 33, p. 863. 



